Hearing aid



FIG. 1 is a perspective view of the hearing aid showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a rear elevation view thereof;

FIG. 7 is a bottom perspective view thereof; and,

FIG. 8 is a bottom plan view thereof.

The broken lines depict portions of the hearing aid that form no part of the claimed design. 

CLAIM The ornamental design for a hearing aid, as shown and described. 